Does bumblebee preference of continuous over interrupted strings in string-pulling tasks indicate means-end comprehension?

Abstract Bumblebees (Bombus terrestris) have been shown to engage in string-pulling behavior to access rewards. The objective of this study was to elucidate whether bumblebees display a means-end comprehension in string-pulling task. We presented bumblebees with tasks involving choosing between two options: one where a string is connected to an artificial flower containing a reward and the other involving interrupted strings. Surprisingly, bumblebees displayed a consistent preference for pulling connected strings over interrupted ones after training with a stepwise pulling technique. Intriguingly, when exposed to novel string colors, bees continued to exhibit a bias towards pulling the connected string. This suggests that bumblebees engage in featural generalization of the visual display of the string connected to the flower in this task. When the bumblebees were confronted with coiled connected strings during the testing phase, they failed to identify and reject interrupted strings. This finding underscores the significance of visual consistency in enabling the bumblebees to perform the task successfully. Our results suggest that bumblebees to distinguish between continuous strings and interrupted strings relies on a combination of image matching and associative learning, rather than means-end understanding. These insights contribute to a deeper understanding of the cognitive processes employed by bumblebees when tackling complex spatial tasks.